hemp fibers

For our first trial, we used the desired Cutting Mill PULVERISETTE 15 for comminution. The mill was equipped with our standard funnel for long and bulk solids. Also a sieve insert with 0,5 mm trapezoidal perforation was used to grind down the sample material.

About one liter of sample (~ 100 grams) was slowly fed into the mill. After three minutes, the complete sample was transferred into the grinding chamber. At this point, already 92 grams of sample output was found inside the collecting vessel. The output rose to 99 grams after a total grinding time of four minutes. Because no further grinding sound was observed, we stopped the mill after four minutes.

Surely a fibrous sample can pass the perforations longitudinal. Up to ~ 2-3 mm long fibers were spotted.

The grinding chamber was cleaned rapidly by vacuuming with a soft brush. If several kinds of sample should be ground on a regular basis, we would recommend using a Universal Cutting Mill PULVERISETTE 19 (for a much faster handling and easy cleaning between each sample type).

With our second trial, we used double of sample amount (~ 2 liters of sample) and equipped the mill with a sieve insert with 0,25 mm trapezoidal perforation.

With the sample pusher, the sample was compressed inside the grinding chamber every now and then. A bit of fine sample dust escaped the feeding funnel during this procedure.

The complete sample was transferred into the grinding chamber within seven minutes. At this point, we found 170 grams of output inside the collecting vessel. After a total grinding time of 9 minutes, the grinding trial was aborted. 185 grams of output was packed. About 10 % of trapezoidal perforations were clogged with fine sample particles.

Surely much higher amounts of sample could be ground this way, before a cleaning step would be required. Majority of residues were removed rapidly by vacuuming with a soft brush. A brass wired brush was used to free the sieve insert.

Also a Variable Speed Rotor Mill PULVERISETTE 14 classic line can be used for comminution of such a sample. Typically, only < 2 cm long particles should be fed into the mill. Longer fragment might bend above the rotor ribs and would not be ground properly.

We used the Impact rotor with 8 ribs made of stainless steel and a sieve ring with 2,0 mm trapezoidal perforation for precutting. The picked sieve ring came with reinforced edges for a much longer durability.

The remaining 120 grams of sample was slowly fed into the mill. The grinding sound was typical without any obstacles. Surely also a sieve ring without enforcement could be used for such a brittle sample, too.

After 2,5 minutes, all sample was successfully fed and ground. Inside the cyclones collecting glass, only fragments < 4 mm max. length were found. No significant residues were left inside the grinding chamber.

Surely much higher amounts of sample could be ground this way, too.

After pre crushing of sample in result three, now the Variable Speed Rotor Mill PULVERISETTE 14 was used for fine grinding. The sieve ring was exchanged against a sieve ring 0,2 mm trapezoidal perforation.

100 grams of precut sample (< 4 mm) were red and ground within five minutes. To automatize feeding, also a Vibratory Feeder LABORETTE 24 can be connected to our Variable Speed Rotor Mill PULVERISETTE 14 classic line, too.

Like our pre grinding trial, also this fine grinding step was showing a smooth grinding sound. After five minutes, no significant residues were found inside the grinding chamber. A small amount of dust remained inside the grinding chamber and was quickly removed by vacuuming with a soft brush.

For an intensive cleaning, also grinding parts can be dissembled without tools and washed with warm water.

The sample output inside the cyclones collecting glass was showing fragments up to 1 mm length, only a few pieces were longer (still < 2 mm max. length). Because the perforations of the sieve ring were not clogged, surely even higher amounts of sample could be ground this way, too.